A chalk line is a string which has been impregnated with chalk dust. Chalk lines are frequently used on construction sites to mark colored lines on ceilings, floors, and walls. Quite often, the colored lines to be marked are of considerable length, consequently requiring a chalk line of considerable length. It is therefore known in the art to store the chalk line in a chalk line holder wound about a spool.
To use the holder, one end of the chalk line is secured to a post by means of a hook, for example, attached to one end of the chalk line. The chalk line holder is then moved away from the secured end of the chalk line to pay the chalk line off of the spool. When a predetermined length of chalk line has been paid off of the spool, the chalk line is held taut and snapped to produce a colored line on the ceiling, floor, or wall.
Once the colored line has been marked on the desired surface, it is necessary to wind the chalk line back onto the spool. U.S. Pat. No. 4,272,036 features a manually-operated crank which moves the spool through an associated gear train. Movement of the crank handle about its axis causes movement of the spool about its axis, causing the chalk line to be wound onto the spool.
There are several disadvantages to using a manually-operated crank system, such as shown in U.S. Pat. No. 4,272,036. Chief among the disadvantages is the effort which the operator must exert in order to get the chalk line wound onto the spool.
To overcome the disadvantages of a manually-operated line-retrieval system, it is known in the art to use an automatic line-retrieval system, such as is shown in U.S. Pat. No. 4,765,557. In U.S. Pat. No. 4,765,557, a spring is used to bias the spool toward a fully wound position, thereby achieving automatic retrieval of the chalk line.
The system of U.S. Pat. No. 4,765,557, however, also has disadvantages. For instance, the speed at which the line is wound onto the spool is not directly controlled by the user, as is the case with the manually-operated system. Instead, the size and strength of the spring directly controls the speed at which the line is wound onto the spool. Additionally, chalk dust must be prevented from entering the automatic retrieval system, and thereby degrading the performance of the automatic retrieval system.
It is known in the art to provide a brake or lock system which the operator can use to indirectly control the speed at which the line is wound onto the spool. For example, U.S. Pat. Nos. 4,565,011; 4,592,148; 4,765,557; and 4,813,145 all provide frictional braking systems wherein a brake surface is pressed against a portion of the spool to limit the speed at which the spool rotates or fix the position of the spool relative to a housing. U.S. Pat. Nos. 4,192,078 and 5,509,616 disclose ratchet/pawl braking systems which can be used to control the rate of retrieval of the line onto the spool. U.S. Pat. No. 5,509,616 also features a centrifugal speed regulator with brake elements bearing against a central arbor to limit the speed or rate of retrieval of the line onto the spool.
With respect to the problem of chalk dust contaminating the automatic retrieval system, it is known in the art to make a chalk line holder having a partition which divides the holder housing into two compartments. A first compartment houses the spool, the chalk line, and the chalk dust for impregnating the chalk line. The second compartment houses a torsion spring which cooperates with the spool to cause the spool to rotate to thereby automatically retrieve the chalk line when tension on the chalk line is released or the braking mechanism is moved to a disengaged position. See, for example, U.S. Pat. Nos. 4,192,708; 4,592,148; and 5,042,159.
It is also known in the art to make a hollow spool which is used to house the torsion spring, with an opening formed in the hollow spool to accept a post which is fixed to the housing. The torsion spring is then attached at one end to the fixed post and at the other end to the inside of the hollow spool. See, for example, U.S. Pat. No. 4,765,557. In addition, it is also known in the art to provide a post which is releasably fixable to the housing, and is associated with the hollow spool. See, for example, U.S. Pat. Nos. 4,813,145 and 5,509,616.